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Zagazig J. Agric. Res., Vol. 51 No. (5) 2024 989
Zagazig J. Agric. Res., Vol. 51 No. (5) 2024 989
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| Abstract: |
ABSTRACT: Survey and population densities of aphidophagous syrphid predators and their insect
hyperparasitoids on maize plants infesting with aphids namely, Rhopalosiphum maidis (Fitch) and
Rhopalosiphum padi (Linnaeus) at El-Deeb village, Abou-Kbeer district, Sharkia Governorate, Egypt
were studied during 2022 and 2023 seasons. The obtained results were summarized as follow: six
species of aphidophagous syrphid belonging to family Syrphidae namely, Xanthogramma aegyptium
Wied., Sphaerophoria flavicauda Zett., Paragus aegyptius Macq., Paragus spp., Metasyrphus
(=Syrphus) corollae (Fabr.) and Scaeva albomaculata Macq were surveyed on maize plants infesting
with aphids. The total relative densities of the syrphid species were 34.17, 23.92, 18.54, 10.36, 7.22
and 5.79 % of the total number of hoverfly, successively. The total numbers of aphidophagous syrphid
predators were fluctuated, showing a distinct peaks of 343 and 371 predators/sample in the 2nd and 3rd
weeks of August during the first and second seasons, consecutively. The highest total monthly counts
of 1016 and 1299 predators recorded in August during two successive seasons 2022 and 2023,
consecutively. The means of syrphids : prey ratio were 1 : 28.76 and 1 : 22.59 during two successive
seasons. Five species of hyperparasitoids belong to four families were recorded parasitized on syrphid
species namely, Telenomus acrobats Giard, Telenomus sp. (Scelionidae), Diplazon laetatorius
(Fabricius) (Ichneumonidae), Syrphophagus aphidivorus (Mayr) (Encyrtidae) and Tetrastichus sp.
(Eulophidae), represented 25.43, 16.38, 25.43, 19.62 and 13.14% of the total collected hyperparasitoids,
successively. The fluctuations of the total parasitoidism percentages recorded one and two peaks of
activity during the first and second seasons, respectively. The mean percentages of parasitoidism
during the second season was relatively low, 17.65 % in comparison with that in the first one
(21.67%). The correlations between the total numbers of aphidophagous syrphid species and
percentages of parasitodism were positive significant during two successive seasons. The periodic
mean temperature and relative humidity affected syrphid species population by 55.27 and 62.57%
during the 1st and 2nd seasons, respectively. Temperature and relative humidity affected percentages of
parasitodism by 51.19 and 47.34 during the 1st and 2nd seasons, consecutively. Generally, the
pesticides are not the only ones that affect on aphidophagous syrphid predators but the
hyperparasitoids decrease the total numbers of the predators and negatively or harmfully affect their
role in the biological control of aphid species in open felids and greenhouses.
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